Pentode-triode plate-coupled one-shot multivibrator



United S -g patm e 2,824,223 PENTODE-TRIODE PLATE-COUPLED ONE-H0 MULTIVIBRATOR Richardson Phelps, Jr., United States Navy, assignor to the United States of America as represented by the Secretary of the Navy Application March 30, 1954, Serial No. 419,940 Claims. (Cl; 250-27) (Granted under Title 35, U. S. Code (1952), sec. 266) This invention relates to a one-shot pentode-triode plate-coupled multivibrator.

The conventional plate-coupled one-shot multivibrator usually employs two triodes. The triggering system employed with this type of multivibrator requires an additional triggering tube and a relatively high positive triggering voltage. In this conventional type of multivibrator circuit there was no Way of isolating the trigger injection circuit from the multivibrator without using a separate triggering tube. a

It is accordingly an object of this invention to provide a multivibrator circuit which allows complete isolation of the trigger input circuit without using a separate triggering tube.

It is a further object of this invention to utilize a triggering pulse of small negative amplitude instead the relatively high positive voltage which is used inconventional multivibrator circuits.

It is still a further object of the invention to present a multivibrator circuit in which the period may be changed by changing one of the inputs to the circuit and without disturbing the constants of the circuit.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a circuit diagram of the pentode-triode oneshot multivibrator.

Fig. 2 is a diagram which pictorially depicts the waveforms of the voltages of various parts of the circuit against a time base.

In Fig. l is shown an arrangement of a triode-pentode plate coupled multivibrator. Triode V and pentode V are cathode coupled and connected to ground. The plates of V and V are connected to a positive voltage E through load resistor RL and RL,, respectively. The plate of V is coupled to the grid of V through capacitor C and the plate of V is coupled to the suppressor grid of V through capacitor C The suppressor grid of V is connected to'a positive source of voltage+Eg through resistor Rg pressed on the grid of triode V through resistor Rg A positive voltage +Eg is impressed on the screen grid of pentode V The trigger input esynch is impressed on the control grid of pentode V through capacitor C The control grid of pentode V is coupled to the cathode of V through resistor Rg The operating values for a typical system will be summarized at the end of this speci- ;ing heavily. The voltages at this time for the various parts of the circuit are depicted by time 10, in Fig. 2. When the negative trigger pulse esynch is applied to the control grid of V through capacitor C the plate current is greatly reduced and the plate voltage of V rises. This :rising plate voltage of pentode V is applied to the grid triode V through capacitor C The increased volt- A negative biasing voltage Eg is im- 2,824,223 Pfatented Feb. 18,1958

ice

age on the grid of triode V causes this tube to start conducting. When triode V starts to conduct the plate voltage of triode V is caused to fall; and this falling voltage is impressed on the suppressor grid of pentode V through capacitor C The negative going voltage on the suppressor grid of V causes further reduction of the plate current in pentode V thereby further raising the plate voltage of V This action in turn further raises the grid voltage of triode V causing more current to flow in V and thereby lowering the plate voltage of triode V This switching action is very rapid and results in V being heavily conducting and V being cut off due to its low suppressor voltage. At this instant of the cycle, the voltages of the various components of the circuit are shown in Fig. 2 at time 11.

At this time 11 the suppressor voltage, eg starts its exponential rise toward voltage Eg with time constant (Rg +RL )(C When the suppressor voltage eg rises to to cut 013? value at time 12, Fig. 2, pentode V starts to conduct. This causes the plate voltage of V to drop which in turn causes the grid voltage of triode V to drop byway of capacitor C As this occurs, the plate voltage of triode V is raised. Since capacitor C couples the plate of triode V to the suppressor grid of pentode V the suppressor voltage of V is raised as the plate voltage of triode V is raised. This process continues rapidly until triode V is cut oil and pentode V is again heavily conducting. This condition is represented by time 13in Fig. 2. The circuit remains in this quiescent condition until the arrival of the next trigger pulse. In Fig. 2 the start of the cycle is at time i=0. The cycle duration is for time, t=T, as shown in the diagram.

The operation of the circuit is stable and is relatively independent of changes in the tubes, components, or operating voltages. Pulse duration can be controlled over a relatively wide range by varying voltage lEg For example, by adjusting Eg so that its voltage is zero without changing the other components of the circuit which are listed at the end of the specification, the period of the circuit is 920 microseconds. At a value of Eg =+250 v. the period equals microseconds. Furthermore, in the described circuit the trigger pulse required. is only from -l.7 to 2.0 volts. The trigger pulse has only to be sufiiciently large to make triode V conduct in order to start the switching action.

It can be readily seen from the above description that the trigger injection through the control grid of the pentode makes the trigger injection circuit entirely independent of the operation of the multivibrator circuit since this construction provides complete isolation of the trigger injection system.

A list of the typical component values for the instant circuit which have been found satisfactory are as follows:

Operating voltages for a period of 780 microseconds: E Volts. Egg +60 volts. Eg 45 volts. Eg +60 volts. -1.7 volts for 60 microseconds. Obviously many modifications and variations of the present invention are possible in the light of the above teachings. .It. is,...there.fore,.to .be unders.tood...that within the scope of the appended claims the invention may be practiced otherwise than asuspecifically described.

The invention; describedghereinrrmayt bennanufaqtured and. usedbyr: or for; the Govennrnennofnthe; United States of: America; for: governmental; purposest wijthout the;paymenh .of ranyrroyal-ties. thereon. or; therefor.

Having ;thus,described my! invention I;.Clairn:

: 1. A;rnultivibraton,oi1-ouiti.=eomprisingaa first-(electronic tube havingrra.cathode,;;plate,uand grid, :-arsecond electronic. tube: having ratcathode,,p1atc,;control grid,, screen grid, and suppressor grid, LSEIid -filfiQli'l'QHiC tubes .being cathode :coupled (to ground 2 and nbeing eplate coupled through load z resistors to; a; positive voltage, rfiaid screen grid being connected: to a :positive vol age; said; uppressor grid beingceupled to the, :plate; :of the first electronic; tube throughra. capaeito r,-,saidt gIidUOfi'thE fi'l'St ielectronic tube being coupled to the plate of the SECOndzBlBQtIQIllC tube througlr'a capacitor; means for; .applying .a negative voltage to the I grid of the? fiIStr-ClfiCtfQHiO tube, means, [for applying I a positive. voltage :to then-suppressor grid,v and meanst for: applying a relativelywlow;:negativevoltage to the: control gridwhen; it-.-is:.-desired,.-to actuate the multivibrator.

..2. A;.-pentode.-triode iplate-couplednrnultivibrator comprising a: trioide-havingm cathode, ,plate, and grid, a pentode having a,.cathode,splate,,control ;grid, .screengrid, and suppressomgrid, meanspcoupling the ,cathodes of the pentode. -vand triode.j-to. ground-means coupling. the; plate of thettriode :to the suppresson grid .of the pentode,,means coupling the :plate, of theepentode; to the-grid :ot thertriode, means for impressing po-sitivevvoltageson the suppressor and screen-; grids of;the;pentode,-,-means for impressing, a negative voltage, oncthe grid ofrthe triode,-,and means for impressing a, relatively small ,negativetrigger voltage on the control; grid oftthe pentodeto cause themulti-vibrator circuit .to produce, the required waveform.

3., A multivibratorcircuit comprising a normally .conducting pentode having a, cathode, eplate, contr.ol grid, screengrid and suppressor, grid,. a :normally non-conductlug triode having .a cathode, -plate,/and grid, said plates beingcoupled to; a positive 'voltage, .said cathodes being coupled .to, ground, a means for impressing positive voltages; on. the, suppressor .and 1 screen grids; of the, pentode, meansrtfor impressing alnegative-voltage;on'the grid of the triode, meansconnecting thqplateof thenpentode to the grid of the triode, means coupling the plate of the triode to the suppressor grid of-,,ther:pen,tode,,and-nieans forzimpressinganegativewtrigger pulseonthe control grid of: the pentodewvhereby ;ther norm,ally conducting pentode becomes,non-conducting and the -.-normallynon-conductingntriodeabegins to conduct.

r4. A one-shot; multivibrator, circuit, comprising a normally conducting pentode having a cathode,.-plate,,-controlsgrid, screen ;gr id,-;- and-suppressor; grid, a: normally non-conductinga-triodeshaving1 ar-cathode, plate and; grid, said cathodes being coupled to ground, said plates being coupled through load resistors to a positive voltage, said screen grid" beingvconnecte'd to a positive voltage, a first capacitor coupling "the plate of the triode to the suppressor grid ofthe pentode, a second capacitor coupling'the plate of theupentode to the grid of the triode, a positive voltage connectedto the suppressor grid through a resistor and means for impressing a relatively small negative trigger voltagewon the .control grid of the pentode whereby the normally conducting pentode is caused to become non-conducting and. the, normally non-conducting triode is caused to' become conducting, the period of conduction of the triode being determined by' the time constant of the load resistor of the;triode, the capacitor couplingthe plate of the triode to ,thensuppressor grid of the pentode, andthe resistancecouplingrthe voltage source to the suppressor grid. of the .pentode, ,and: thetnagnitudev of. the last mentioned voltage.

,5Anneshotmul ivibrator.comprisin lat rstncrma ly non-conducting electronic tube having a cathode, plate, and grid, a second normally conducting electronic tube having at least a cathqdg plate, control grid, and supp ifi fi lg l dn sai :cathode 'rbeigg scuttled stomac lather and to ground, said:platesgbeing connected to a positive voltggetthr u sl a res stors: l firs apac c esenne ing th :plat ro nth riirs ;rtub rt ut e uppre so rg i r the second tube, a second capacitor.:connecting the-plate f hesecondrtubeatqrh agri nc th iiir tvtubea. V ro voltage connectedto-said suppressor ;g rid across a resistorrsai creengrid h iua connected .t ,-a,pqsi iye;voltage and means for applying a relativelysmall, negative trigger-pulse-.lto*the-eontrol-"grid of the second tube to cause said first tube to conduct, ithelength of-timeof conduction o'f said"-l irst -tube-bei ngdetermined by the; time constant formed by the load resistor of saidflfirst' tube, the capacitor and= the--resistor connecting said positive voltage-toshid-:suppreSson'grid; and by' the magnitude of said last mentioned-voltage.

6. -A one-shotmultivibrator-comprising a normally con- 'duct-ingfirstelectron-tube havingat' least a cathode, plate, control grid, and a suppressor grid, a normally nonconducting--second electron'tubehavingat least a cathode, -plate, -and-grid; rneans' eoupling "the; plate of 'the'ifirstlube to the-g 1'id-of-'the '-sec-ond --tube, -a capacitor coupling: the plate of the second tube to the suppressor grid-of-the' first -tube, the plates of the tubes beingcoupled'to a positive -voltage,=':the cathodes-beingcoupled toground, said screen --grid b'eing connected toa positive voltageand the control grid of the first tube being-coupled=-toasourcegfor supplying -rela tivelysmall negative voltage pulses thereto i for actuating =the-wmultivibrator' circuit whereby the normallyconductingtube -becomes non-conductirig and the normally non-conducting tube-conducts, and a voltage impressed on-saidsuppressor gridgthe magnitude of said-voltage determining thenperiod-ofthe multivibrator.

*7. A one-shot-multivibrator comprising a --normally non-condudting-thiode =having -a cathodefplate and I grid and a normally conduoting--pentode-having a-;ca'thode, plate control grid screen grid,--.and suppressor grid; sa id cathodes coupled to ground and said -plates coupled through load resistors to a: positive voltage,--'the;plate' of the ypentode being reactive-coupled to the grid of 1 the triode, capacitive means coupling the plate ofl-thejriode to'the suppressor-grid of-the-pentode, saidsc-reen grid'being connected to aposit-ivevoltage, e a relatively small negative avoltage pulsecoupled to--another grid "of the pentodeior causingisaid pen-tode'to cease conducting and to cause saida-triode-to conduct; the lengthof timeof conductionr-ofi t-he; triode 'heing *dependent on the value of {the"capacitiveemeans.

8. A-.rnultivihrator as set -forth'-in-c1aim1'7 wherein a vsecond voltage is-impressed -0n thegrid of the-pentode to which theplaterofi thentriode is coupled, the rnagnitude of said voltage further determiningthe lengthof time of conduction -.of the :triode.

':;9. Au multiyibratoraas recited in: claim 1 7 wherein the capacitatives means formma :part of a-- irc'sistancecapaci- .tance :oircuit lwhioh'rlhasr a predetermined time constant;

'10; A-amultiyibrator 'assset forth inclaim 9- ewherein -a secondruoltageris impressedton thegrid of the pentode; to which the plate of the triode is coupled, the magnitudeof saidnvoltagetifugthersndetermining tires-length of -time of conduction of: tthe ltriode. 

